Lucky symbols such as daruma dolls and maneki-neko already carry familiar ideas such as wishes coming true, business success, and good fortune. That makes them easy to use in characters, packaging, and other commercial designs.
A completely new character has to build its image from scratch. Lucky symbols do not. A daruma is already associated with wishes and success, while a maneki-neko is linked with luck and prosperity in business.
Because of that, a product or advertisement can use the appearance of a lucky symbol and immediately bring those associations with it.
Lucky symbols have also long been part of everyday life and business in Japan. Maneki-neko are placed in shops, while daruma are bought for wishes and personal goals. They are not objects that belong only in solemn or religious settings, so seeing them on packaging or in advertising does not necessarily feel out of place.
Another reason they work well in commercial design is that their shapes can be changed quite a lot without losing their identity. A daruma can be given arms and legs, or a maneki-neko can be redrawn in a cute style, and people can still recognize what it represents as long as some key features remain.
Changing the design itself is not automatically disrespectful either. The line is more likely to be crossed when the original lucky symbol is clearly being mocked or used in an insulting way.
Lucky symbols are easy to adapt because ideas such as good fortune and success are already widely associated with them, and those associations can survive even when the design changes.
